Our aim is to define the mechanisms which control skeletal muscle fiber diversity. Human skeletal muscles function in locomotion and posture, and many myopathies affect one group of muscles over another. However relatively little is known of how genetically similar myoblasts contribute to muscles with distinct physiological phenotypes. Elucidating mechanisms that control tissue-specific development will be helpful in designing rational therapies for muscle-related diseases. This research will focus on the development of diversity in the muscles of Drosophila. The adult thorax contains two muscle types which are distinguishable morphologically, biochemically and in muscle protein isoform usage. To determine how distinct muscles arise we shall identify factors controlling the transcriptional regulation of two fiber-specific genes. We shall also determine the roles of signaling molecules in the generation of fiber diversity, by ectopically expressing particular signals and assaying the fiber types resulting. This will be used in combination with screens to identify loci which specify particular muscles. These findings will contribute to understanding how mesodermal cells are specified to give rise to diverse muscle types, and how different factors induce diversity in muscles. Extensive research has already proven that the mechanisms controlling myogenesis are highly conserved through evolution, therefore the identification of factors controlling muscle fiber diversity in Drosophila will be highly relevant to our understanding of myogenesis in vertebrates.